[The operation line can specify three optional register variables:
The first (called [maxkey] in this example)
receives the maximum key number found in the document file.
The second (called [ncols] in this example
receives the number of columns in use in the document file.
The third (called [nkeys] in this example)
receives the number of keys in use in the document file.]
.DOCUMENT FILE: DOC555
[Enter the name of an existing document file.]
[In the example let's say the document file has the first
490 keys filled then skips nine keys and fills key number 500
and the maximum number of columns in the
document file is 4. The operation listed above will set
[maxkey] to: 500, [ncols] to: 4, and [nkeys] to: 491.